Although antidepressant and antipsychotic utilization by gestational trimester has been described, longitudinal prescription patterns within pregnancies have received less attention. All mothers in the Clinical Practice Research Datalink's Mother Baby Link enrolled from 6months before pregnancy to 3months after delivery, with delivery date between 01/1989 and 12/2010 were included (n=421,645). Drug use prevalence was calculated as the number of women with prescriptions for antidepressants or antipsychotics in capsules/tablets in the 3months before pregnancy (T0), the first (T1), second (T2), or third (T3) pregnancy trimesters, or the 3months after delivery (T4). In each pregnancy, prescriptions in T0 and T3 were compared to identify treatment discontinuation, simplification (some drugs discontinued or dose lowered), no treatment change, intensification (drugs added to prior treatment or dose increased), and start. Antidepressant use in T0 through T4 was 4.69, 2.81, 1.31, 1.34, and 5.46%, respectively. Of 19,774 T0 antidepressant users, 79.57% discontinued, 5.13% simplified, 9.06% did not change, and 2.19% intensified treatment. 0.40% of non-users in T0 started antidepressants by T3. Antipsychotic use in T0 through T4 was 0.57, 1.34, 0.54, 0.28 and 0.38%. Excluding prochlorperazine, it was 0.15, 0.13, 0.08, 0.07 and 0.15%, respectively; of 639 T0 users, 72.30% discontinued, 7.51% simplified, 11.11% did not change, and 4.07% intensified treatment. 0.03% of non-users in T0 started antipsychotics by T3. Cross-sectional and longitudinal analyses identified a post-conception decrease in antidepressant and antipsychotic prescribing. Longitudinal treatment assessment additionally captured several treatment patterns among those who do not discontinue treatment that usually stay unrecognized.